Fluid-pressure hoist.



Patented Dec. 3|, |90l.

G SCHUHMANN num Pnss'sune Hom.

(Application led Sapt. 23, 1901.)

anonimos.,

lhvirlsio Smarts FFICE.

GEORGE SCHUHMANN, OF READING, PENNSYLVANIA.

FLUID-PRESSURE'. HOIST.

SPECIFICATION forming part of Letters Eat-,ent No. 689,918, dated December 3l, 1901.

Application filed September 23, 1991. Serial No. 76,197. (No model.)

To all whom it may concern:

Be it known that I, GEORGE SCHUHMANN, a citizen of the United States of America, and a resident of Reading, in the county of Berks and State of Pennsylvania, have invented certain new and useful Improvements in Fluid- Pressure Hoists, of which the following is a specification.

My invention relates particularly to fluidpressure hoists in which it is desirable that the load shall be yieldingl y suspended-such, for instance, as are employed to suspend forgings while subjecting them to the blows of a steam-hammer, the effect of which is ordinarily to produce objectionable shock to the mechanism. A main purpose of my invention is to avoid such shocks while at the same time maintaining constant and positive control of the load; and the invention consists in employing simultaneously an elastic and an inelastic pressure fluid, the former being utilized to support the load by pressing upward upon a carrying-piston and the latter being utilized upon the upper end of said piston to oppose the lifting action of the elastic fluid and to positively regulate the latter as desired.

The invention is fully described in connection with the accompanying drawings and is specifically pointed out in the claims.

Figure l indicates diagrammatic-ally a complete apparatus embodying my invention as applied to a crane, on the swinging arm of which the hoisting mechanism is carried. Figs. 2, 3, and 4 indicate different positions of the regulating-valve which controls the hydraulic action above the piston.

A represents the vertical post of a crane, and B the swinging arm or jib of the saine, to which the hoisting-cylinder C is secured in vertical posit-ion. rlhis cylinder may be provided with any suitable piston D, having a depending rod CZ, which passes through a stuffing-box ein the lower cylinder-head E and which :is arranged at its lower end as desired to engage the load to be carried. Fluidsupplying pipes F and G connect,respectively, with the upper and lower ends of the cylinder, the former, as indicated, somewhat below the top cylinder-head H, so as to provide a space above its inlet to the cylinder, which may be utilized as an air-chamber above the inelastic fluid supplied to the cylinder through said pipe F, as hereinafter explained. This pipe F in the present construction is carried downward through the hollow lower journal of the crane-post and communicates through a fixed extension-pipe F with a liquid-pressure reservoir, while the supply-pipe G to the lower end of the cylinder extends in like manner, as indicated, through the hollow upper journal of the crane-post and communicates through a fixed pipe G with a compressed-air reservoir. These two reservoirs or sources of liquid-pressure and air-pressure may be entirely independent; but in theconstruction i11- dicated they are combined in a single pressure tank oraccuniulator J, adapted to supply both liquid-pressure and air-pressure. This is accomplished by connecting the pipe F Fl to the lower portion of said pressure-tank, so as to communicate with the liquid-space thereof, and the pipe G G with the upper or air-space portion. A uniform hydraulic and air pressure is maintained in the tank J by means of a pump K and governor M therefor, said pressure, which is freely communicated to the under side of piston D, being sufficient to carry the maximum load for which the hoist is intended. The hydraulic pressure which is conveyed through pipes F F to the top of the piston is in the construction indicated just equal per square inch of surface to the compressed air pressure beneath, though owing to the reduction of the latter surface by the piston-rod an actual excess of downward pressure may be exerted on the piston. The iiow of liquid is conveniently controlled by means of a three-way valve for the pipe F, as shown in Figs. 2, 3, and 4t, in which the rotary valve P is indicated in diferent positions in the case V. In Fig. 1 the pressure liquid is in free communication with the top of the hoisting-cylinder, which position will cause the lifting pressure of the air upon the lower surface of the piston to be entirely neutralized and practically over-balanced, so as to positively lower the unloaded piston..

When the valve is turned to the position indicated in Fig; l, the cylinder is put in communication with the exhaust-port 3 and pipe X to allow the escape of the liquid from above the piston, thus permitting the air-pressure below to raise the piston and load as rapidly as the escape of liquid permits, but no faster. When the load has been raised to the desired height, the turning of the valve to the posi- .tion indicated in Fig. 3 will immediately stop it, the exhaust of liquid being shut oi. The load will then be supported upon the elastic compressed air, so as to permit of its yielding without shock to any strain, such as the blow of a hammer or a temporary overload, while at the same time its upward movement is as positively controlled as in a hydraulic apparatus. Owing, however, to the liability of shocks resulting from the quick return of the.

piston against the liquid above after a temporary downward strain such as referred to or because of the too-sudden shutting off of the exhaust while lifting I prefer to provide, in connection with the inelastic liquid above the piston, a cushion for the latter which will slightly modify without materially changing the positive stopping action of the latter under such conditions. This maybe veryeasily secured by the simple construction indicated and already referred to, which provides an air-chamber c in the cylinder above the opening of pipe F.

While it is common to employ either hydraulic pressureor compressed air in the operation of hoisting mechanism, it will be observed that my invention involves a new method of operation combining the advantages of each medium, so as to practically eliminate their respective disadvantages, the load being carried upon an elastic medi.um,yet having its movement positively controlled by an inelastic medium, the unyielding action of which latter may be modified', if desired, without materially affecting the accuracy of movement secured thereby in connection with elasticity of support.

It will be understood that while the single pressure-tank system specifically described `is frequently preferable, yet my invention is not limited to such an arrangement, as the pipes F and Gr may connect With independent sourcesof hydraulic and air pressure,

respectively, the available hydraulic pressure being at least equal to the air-pressure and preferably somewhat in excess of it, so as to insure the positive lowering of the nnloaded piston, notwithstanding the frictional resistance to such movement.

The simplicity of the apparatus and of its operation, as well as its advantages, will be readily seen.

What I claim isl. The combination With sources of compressed-air and liquid pressure, of a hoistingcylinder having a load-carrying piston therein, the lower portion of said cylinder being in communication with the compressed-air reservoir and the upper portion in valve-controlled communication with'the liquid-pressure reservoir and with a discharge-outlet substantially as set forth.

2. The combination with a hoisting-cylinder and a load-carrying piston therein, of a liquid-pressure reservoir or tank having a confined-air space therein arranged in communication with the lower portion of said cylinder and the liquid-space of the same arranged in valve-controlled communication with the 'upper portion of said cylinder substantially as set forth.

3. The combination with sources of compressed-air and liquid pressure, of a hoistingcylinder having a load-carrying piston therein, the lower portion of said cylinder being in communication with the compressed-air reservoir and the upper portion in valve-controlled communication with the liquid-pressure reservoir and with a discharge-outlet and provided With a cushioningchamber above said liquid communication, substantially as set forth.

Signed at Reading, Pennsylvania, this 20th day of September, 1901.

GEORGE soi-IUIIMANN.`

Witnesses:

HEBER Y. YosT, JEFFERSON SNYDER. 

